A catheter includes an elongate slender flexible portion for insertion into a body cavity such as a vein or artery. The elongate portion has at least one lumen, but typically has a plurality of lumens, and extends from a proximal end at a coupling element to a distal end, which in use is inside the human or animal body. The lumens within the elongate portion can be used to introduce or remove fluid from the human or animal body or alternatively carry means allowing measurement of blood pressure, blood flow or such like. As each lumen typically contains different means performing different functions, the means within each lumen may be attached to particular components or equipment. The means within each lumen within the elongate portion are connected to particular components or equipment via extension tubes, which attach to the proximal end of the lumens of the elongate portion via the coupling element.
The extension tubes are commonly attached to the proximal end of the lumens of the elongate portion via plastic adapters. These plastic adapters may be glued in position using adhesive such that the adhesive bonds the extension tube to the elongate portion. However this method of gluing adapters to the extension tube is very labour intensive and requires long drying times for the adhesive to set and harden. Further, the adhesive may flow into one or more of the lumens of the elongate portion and completely or partially block the lumens.
An alternative method used, that eliminates the need for gluing, is the insertion of wire mandrels through an extension tube and into a lumen of the elongate portion. A mould tool is then placed around the elongate portion and extension tube and a coupling element formed by moulding plastic into the mould tool. The coupling element formed around the extension tube and the proximal end of the elongate portion, secures the extension tube to the elongate portion. Removal of the wire mandrels from the lumens of the elongate portion and from the extension tube creates passages in the coupling element allowing passage of fluid or other means from the extension tube into the lumens of the elongate portion.
This alternative method of attaching the extension tubes to the elongate member also has a number of disadvantages in that large diameter extension tubes or elongate portions tend to melt in the mould, while small diameter extension tubes or elongate portions allow the plastic being moulded to “flash” out of the mould alongside the extension tubes or elongate portions. In addition the hot plastic used for moulding can cause kinking or collapse of the lumens within the elongate portion.
The moulding method described above to attach the extension tubes to the elongate portion has been improved by including an insert element in the catheter as described in U.S. Pat. No. 4,670,009. The insert element of the catheter surrounds the extension tubes, holding the extension tubes in place in the finished catheter and preventing the injected plastic from “flashing” out around the extension tubes during the moulding process. During manufacture the use of an integral insert element in the catheter means the mould need not be sized to accommodate any particular number or diameter of extension tubes, provided the mould can close off around the insert element such that no plastic flashes through the moulding insert interface.
The use of an insert element which is incorporated into the final catheter product to secure the extension tubes to the elongate element requires that the integral insert element is pre-fabricated for each catheter being produced. The fabrication of an integral insert element adds to the cost of the production of the catheter. Further the use of an integral insert element in the catheter adds to the number of components and material within the catheter and this again contributes to the production cost of the catheter.
It would be advantageous if a catheter could be produced which did not require an integral insert element to be fabricated for and included in each catheter produced. The use of a releasable insert element(s) or an insert element integral to the mould tool would be advantageous as the use of such an insert would reduce the expense of fabrication of the catheter and further reduce the cost of the material required to make the catheter.